Embodiments of the present invention relate to a method for exposing a layer buried in a substrate.
Exemplarily, a layer, such as, for example, a buried metallic contact pad, in a substrate, such as, for example, in a wafer, is exposed here so as to be able to produce electric contact from the back side to the exposed layer.
Conventionally, contacting of this kind is done by opening the back side of the substrate by means of etching. A wet-chemical etching method, exemplarily using TMAH (tetra methyl ammonium hydroxide), in silicon wafers or a dry-etching method, such as, for example, reactive ion etching, corresponding to the Bosch process is exemplarily used here. Wet-chemical etching is plane-selective so that the patterns may also be adjusted well in the trench to be etched. Additionally, due to the high flank angle of 40-50°, it is also possible to adapt the patterns within the trench by means of lithography. This is based on the fact that depositing a photoresist, for example by means of a spray coating process, is possible starting from a sufficiently wide trench or sufficiently large flank angle, which is the prerequisite for lithography. However, the large flank angle is also of disadvantage since much space is required per trench, depending on the thickness of the substrate. In the dry-etching processes mentioned before, a large aspect ratio is possible such that deep trenches may also be generated at smaller a surface consumption, however, processing the patterns in the trenches is not possible or only to a limited degree due to the lacking or poor suitability for lithography. Consequently, there is demand for an improved approach.